Body composition Flashcards
What is body composition?
=The body’s relative amounts of fat and lean body tissue (fat free mass)
What are the components of fat free mass?
-Muscle
-Bone
-Water
-Organ tissues
Formula to calc total body fat?
Essential fat + storage fat
What is the purpose of essential fat and where is it located
-required for normal physiological function
-Is fat within major organs, muscle and CNS
Difference in essential fat between male and females
-Women have more essential fat (12%) compared to males (3%)
What is storage fat?
-Nonessential fat stored as adipose tissue near the body’s surface
What is % body fat?
-% of total body weight that is fat
-is primary way to evaluate body composition
How to calc fat free mass?
Body mass- fat mass
Why is body composition measured?
-to help assess health risks and determine needed behaviour changes for optimal health
-to help athletes determine the best body composition for performance in their sport
Effects of too little body fat?
-reproductive disorders
-circulatory disorders
-immune disorders
Effects of too much body fat?
-cardiovascular disease
-hypertension
-type 2 diabetes
-cancer
What is a 2 compartmental model of body comp
-splits body into fat free mass and fat mass and suggests one of these components is determined and the other is estimated from the result
What is a 3 compartmental model of body comp
Includes bone mineral content in addition to fat free and fat mass
What is a 4 compartmental model of body comp
Also includes total body water
What are the different methods used to assess body composition?
-height; weight and BMI
-waist to hip ratio
-hydrostatic weighing
-skin fold measurements
-air displacement plethysmography
- dual x ray absorptiometry (DEXA)
-bio electrical impedance analysis (BIA)
How to measure height?
-use stadiometer
-ensure participant removes shoes, stands up straight with heels together and holds deep breath during measurement
How to measure weight?
-measure on calibrated scale
-ensure subject removes shoes and wears minimal clothing (nude if possible)
BMI formula/ healthy ranges
=weight (kg) / height (m2)
-underweight <18.5
-normal 18.5- 24.9
-overweight 25-29.9
-obese 30-34.9
Extremely obese 35<
How to measure wait to hip ratio
-waist circumference- measured at narrowest point below ribs
-hip circumference- measured at widest point
How to measure using skin fold tests
-multiple sights are measured and % BF is calculated using some of sites
-measurements should be taken on right side of body
What is used when performing skin folds and in what 2 ways can they be used?
-used callipers to measure thickness of double layer of skin
-used to track changes in individuals or sum of the skin folds or sum of multiple skin fold sites can be used with equation to calc % body fat
Limitations of skin fold tests
-possible technician error
-skinfold thickbess can be affected by factors other than amount of fat: excercise increases skin thickness, dehydration reduces it, dermatitis increases it
What are the 2 2 compartmental models?
-air displacement plethysmography
-BIA
How does air displacement plethysmography work
-calculated %BF from body density and uses computerised air pressure sensors to determine amount of air displaced while participant is in bod pod
How does BIA work
-rapid, non invasive and inexpensive
-sends electrical current thru body to estimate body fat (based on idea that fat is less conductive than lean tissue)
Describe how DEXA works
- is a 3 compartmental model
-used a series of low dose radiation scans providing high accuracy
-provided measurements of bone mineral, fat and non bone lean tissue
Hydro-densitometry method?
-2 compartmental and indirect
Hydro-densitometry method pros and cons
+can be accurate when carried out by qualified person
-assumption of specific tissue densities (differ in
elite athletic populations)
- residual lung volume can be a source of error
- Claustrophobia/fear whilst underwater
- Expensive equipment. Needs maintenance,
sterilisation and cleaning
- cannot measure distribution of FFM or FM
- air can be contained within an individual’s
swimsuit, skin, head, body hair, digestive
tract…leads to false estimations
- air temperature, barometric pressure, nitrogen
analyser and force sensor calibrations all can lead
to measurement error
- is time consuming and needs expertise.
Air displacement plethysmography pros and cons?
+Overcomes several of the aforementioned
limitations of hydro-densitometry
+ Reliable
- Not sensitive enough for changes in elite
athletic body composition
-Too sensitive to clothing, body hair, air
movement, moisture, pressure and
temperature changes
-expensive to buy equipment.
-Overestimates BF% compared with hydro-
densitometry
- Body fat measures diverge at the extremes of
the BMI spectrum (concern in certain athletic
populations)
- cannot measure distribution of FFM or FM
BIAS pros and cons?
+ Speed
+ minimal expertise required
+ portability
+ cost (compared to other methods)
-Can be affected by temperature and hydration
status
-sensitivity to conductive surface of electrodes and
electrode placement
- Assumptions on the composition of the body in
formula and calculations, irrespective of population group
-the limbs contribute a large proportion to whole-
body impedance, despite the relatively low
contribution to overall BM [31].
- Limited validation in athletic populations
-Some under and overestimation of FFM
-There is also large variability between devices
Ultrasound pros and cons
-is multi compartmental
+ Reliable and accurate measure of subcutaneous
adipose tissue thickness
+ MAY be portable*
- Affected by the chosen frequency, pressure
and orientation of the probe causing
measurement error
-Requires technician expertise
-Can be expensive and impractical within the
applied setting, even with improved
portability
DEXA pros and cons
-is multi compartmental
+ Reliable measure of body composition
+Measures Bone Mineral Content (low energy
availability etc)
+ Limb-specific estimations of FM and FFM which
can be useful when tracking injured athletes
-Uses radiation: legal and ethical constraints
(approval by doctor /national ethics committee)
- Requires trained and certified technician
- Variations between manufacturers (energy levels
emitted, pixel size, software algorithms etc)
-Expensive equipment
-Not portable
-Time consuming
-Not reliable at extremes of size (very large people)
- Affected by water and glycogen levels
